xref: /freebsd/sys/amd64/amd64/mp_machdep.c (revision 9768746b)
1 /*-
2  * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
3  *
4  * Copyright (c) 1996, by Steve Passe
5  * Copyright (c) 2003, by Peter Wemm
6  * All rights reserved.
7  *
8  * Redistribution and use in source and binary forms, with or without
9  * modification, are permitted provided that the following conditions
10  * are met:
11  * 1. Redistributions of source code must retain the above copyright
12  *    notice, this list of conditions and the following disclaimer.
13  * 2. The name of the developer may NOT be used to endorse or promote products
14  *    derived from this software without specific prior written permission.
15  *
16  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
17  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
18  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
19  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
20  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
21  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
22  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
23  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
24  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
25  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
26  * SUCH DAMAGE.
27  */
28 
29 #include <sys/cdefs.h>
30 __FBSDID("$FreeBSD$");
31 
32 #include "opt_acpi.h"
33 #include "opt_cpu.h"
34 #include "opt_ddb.h"
35 #include "opt_kstack_pages.h"
36 #include "opt_sched.h"
37 #include "opt_smp.h"
38 
39 #include <sys/param.h>
40 #include <sys/systm.h>
41 #include <sys/bus.h>
42 #include <sys/cpuset.h>
43 #include <sys/domainset.h>
44 #include <sys/kdb.h>
45 #include <sys/kernel.h>
46 #include <sys/ktr.h>
47 #include <sys/lock.h>
48 #include <sys/malloc.h>
49 #include <sys/memrange.h>
50 #include <sys/mutex.h>
51 #include <sys/pcpu.h>
52 #include <sys/proc.h>
53 #include <sys/sched.h>
54 #include <sys/smp.h>
55 #include <sys/sysctl.h>
56 
57 #include <vm/vm.h>
58 #include <vm/vm_param.h>
59 #include <vm/pmap.h>
60 #include <vm/vm_kern.h>
61 #include <vm/vm_extern.h>
62 #include <vm/vm_page.h>
63 #include <vm/vm_phys.h>
64 
65 #include <x86/apicreg.h>
66 #include <machine/clock.h>
67 #include <machine/cputypes.h>
68 #include <machine/cpufunc.h>
69 #include <x86/mca.h>
70 #include <machine/md_var.h>
71 #include <machine/pcb.h>
72 #include <machine/psl.h>
73 #include <machine/smp.h>
74 #include <machine/specialreg.h>
75 #include <machine/tss.h>
76 #include <x86/ucode.h>
77 #include <machine/cpu.h>
78 #include <x86/init.h>
79 
80 #ifdef DEV_ACPI
81 #include <contrib/dev/acpica/include/acpi.h>
82 #include <dev/acpica/acpivar.h>
83 #endif
84 
85 #define WARMBOOT_TARGET		0
86 #define WARMBOOT_OFF		(KERNBASE + 0x0467)
87 #define WARMBOOT_SEG		(KERNBASE + 0x0469)
88 
89 #define CMOS_REG		(0x70)
90 #define CMOS_DATA		(0x71)
91 #define BIOS_RESET		(0x0f)
92 #define BIOS_WARM		(0x0a)
93 
94 #define GiB(v)			(v ## ULL << 30)
95 
96 #define	AP_BOOTPT_SZ		(PAGE_SIZE * 4)
97 
98 /* Temporary variables for init_secondary()  */
99 static char *doublefault_stack;
100 static char *mce_stack;
101 static char *nmi_stack;
102 static char *dbg_stack;
103 void *bootpcpu;
104 
105 extern u_int mptramp_la57;
106 extern u_int mptramp_nx;
107 
108 /*
109  * Local data and functions.
110  */
111 
112 static int start_ap(int apic_id, vm_paddr_t boot_address);
113 
114 /*
115  * Initialize the IPI handlers and start up the AP's.
116  */
117 void
118 cpu_mp_start(void)
119 {
120 	int i;
121 
122 	/* Initialize the logical ID to APIC ID table. */
123 	for (i = 0; i < MAXCPU; i++) {
124 		cpu_apic_ids[i] = -1;
125 	}
126 
127 	/* Install an inter-CPU IPI for cache and TLB invalidations. */
128 	setidt(IPI_INVLOP, pti ? IDTVEC(invlop_pti) : IDTVEC(invlop),
129 	    SDT_SYSIGT, SEL_KPL, 0);
130 
131 	/* Install an inter-CPU IPI for all-CPU rendezvous */
132 	setidt(IPI_RENDEZVOUS, pti ? IDTVEC(rendezvous_pti) :
133 	    IDTVEC(rendezvous), SDT_SYSIGT, SEL_KPL, 0);
134 
135 	/* Install generic inter-CPU IPI handler */
136 	setidt(IPI_BITMAP_VECTOR, pti ? IDTVEC(ipi_intr_bitmap_handler_pti) :
137 	    IDTVEC(ipi_intr_bitmap_handler), SDT_SYSIGT, SEL_KPL, 0);
138 
139 	/* Install an inter-CPU IPI for CPU stop/restart */
140 	setidt(IPI_STOP, pti ? IDTVEC(cpustop_pti) : IDTVEC(cpustop),
141 	    SDT_SYSIGT, SEL_KPL, 0);
142 
143 	/* Install an inter-CPU IPI for CPU suspend/resume */
144 	setidt(IPI_SUSPEND, pti ? IDTVEC(cpususpend_pti) : IDTVEC(cpususpend),
145 	    SDT_SYSIGT, SEL_KPL, 0);
146 
147 	/* Install an IPI for calling delayed SWI */
148 	setidt(IPI_SWI, pti ? IDTVEC(ipi_swi_pti) : IDTVEC(ipi_swi),
149 	    SDT_SYSIGT, SEL_KPL, 0);
150 
151 	/* Set boot_cpu_id if needed. */
152 	if (boot_cpu_id == -1) {
153 		boot_cpu_id = PCPU_GET(apic_id);
154 		cpu_info[boot_cpu_id].cpu_bsp = 1;
155 	} else
156 		KASSERT(boot_cpu_id == PCPU_GET(apic_id),
157 		    ("BSP's APIC ID doesn't match boot_cpu_id"));
158 
159 	/* Probe logical/physical core configuration. */
160 	topo_probe();
161 
162 	assign_cpu_ids();
163 
164 	mptramp_la57 = la57;
165 	mptramp_nx = pg_nx != 0;
166 	MPASS(kernel_pmap->pm_cr3 < (1UL << 32));
167 	mptramp_pagetables = kernel_pmap->pm_cr3;
168 
169 	/* Start each Application Processor */
170 	start_all_aps();
171 
172 	set_interrupt_apic_ids();
173 
174 #if defined(DEV_ACPI) && MAXMEMDOM > 1
175 	acpi_pxm_set_cpu_locality();
176 #endif
177 }
178 
179 /*
180  * AP CPU's call this to initialize themselves.
181  */
182 void
183 init_secondary(void)
184 {
185 	struct pcpu *pc;
186 	struct nmi_pcpu *np;
187 	struct user_segment_descriptor *gdt;
188 	struct region_descriptor ap_gdt;
189 	u_int64_t cr0;
190 	int cpu, gsel_tss, x;
191 
192 	/* Set by the startup code for us to use */
193 	cpu = bootAP;
194 
195 	/* Update microcode before doing anything else. */
196 	ucode_load_ap(cpu);
197 
198 	/* Initialize the PCPU area. */
199 	pc = bootpcpu;
200 	pcpu_init(pc, cpu, sizeof(struct pcpu));
201 	dpcpu_init(dpcpu, cpu);
202 	pc->pc_apic_id = cpu_apic_ids[cpu];
203 	pc->pc_prvspace = pc;
204 	pc->pc_curthread = 0;
205 	pc->pc_tssp = &pc->pc_common_tss;
206 	pc->pc_rsp0 = 0;
207 	pc->pc_pti_rsp0 = (((vm_offset_t)&pc->pc_pti_stack +
208 	    PC_PTI_STACK_SZ * sizeof(uint64_t)) & ~0xful);
209 	gdt = pc->pc_gdt;
210 	pc->pc_tss = (struct system_segment_descriptor *)&gdt[GPROC0_SEL];
211 	pc->pc_fs32p = &gdt[GUFS32_SEL];
212 	pc->pc_gs32p = &gdt[GUGS32_SEL];
213 	pc->pc_ldt = (struct system_segment_descriptor *)&gdt[GUSERLDT_SEL];
214 	pc->pc_ucr3_load_mask = PMAP_UCR3_NOMASK;
215 	/* See comment in pmap_bootstrap(). */
216 	pc->pc_pcid_next = PMAP_PCID_KERN + 2;
217 	pc->pc_pcid_gen = 1;
218 
219 	pc->pc_smp_tlb_gen = 1;
220 
221 	/* Init tss */
222 	pc->pc_common_tss = __pcpu[0].pc_common_tss;
223 	pc->pc_common_tss.tss_iobase = sizeof(struct amd64tss) +
224 	    IOPERM_BITMAP_SIZE;
225 	pc->pc_common_tss.tss_rsp0 = 0;
226 
227 	/* The doublefault stack runs on IST1. */
228 	np = ((struct nmi_pcpu *)&doublefault_stack[DBLFAULT_STACK_SIZE]) - 1;
229 	np->np_pcpu = (register_t)pc;
230 	pc->pc_common_tss.tss_ist1 = (long)np;
231 
232 	/* The NMI stack runs on IST2. */
233 	np = ((struct nmi_pcpu *)&nmi_stack[NMI_STACK_SIZE]) - 1;
234 	np->np_pcpu = (register_t)pc;
235 	pc->pc_common_tss.tss_ist2 = (long)np;
236 
237 	/* The MC# stack runs on IST3. */
238 	np = ((struct nmi_pcpu *)&mce_stack[MCE_STACK_SIZE]) - 1;
239 	np->np_pcpu = (register_t)pc;
240 	pc->pc_common_tss.tss_ist3 = (long)np;
241 
242 	/* The DB# stack runs on IST4. */
243 	np = ((struct nmi_pcpu *)&dbg_stack[DBG_STACK_SIZE]) - 1;
244 	np->np_pcpu = (register_t)pc;
245 	pc->pc_common_tss.tss_ist4 = (long)np;
246 
247 	/* Prepare private GDT */
248 	gdt_segs[GPROC0_SEL].ssd_base = (long)&pc->pc_common_tss;
249 	for (x = 0; x < NGDT; x++) {
250 		if (x != GPROC0_SEL && x != GPROC0_SEL + 1 &&
251 		    x != GUSERLDT_SEL && x != GUSERLDT_SEL + 1)
252 			ssdtosd(&gdt_segs[x], &gdt[x]);
253 	}
254 	ssdtosyssd(&gdt_segs[GPROC0_SEL],
255 	    (struct system_segment_descriptor *)&gdt[GPROC0_SEL]);
256 	ap_gdt.rd_limit = NGDT * sizeof(gdt[0]) - 1;
257 	ap_gdt.rd_base = (u_long)gdt;
258 	lgdt(&ap_gdt);			/* does magic intra-segment return */
259 
260 	wrmsr(MSR_FSBASE, 0);		/* User value */
261 	wrmsr(MSR_GSBASE, (uint64_t)pc);
262 	wrmsr(MSR_KGSBASE, 0);		/* User value */
263 	fix_cpuid();
264 
265 	lidt(&r_idt);
266 
267 	gsel_tss = GSEL(GPROC0_SEL, SEL_KPL);
268 	ltr(gsel_tss);
269 
270 	/*
271 	 * Set to a known state:
272 	 * Set by mpboot.s: CR0_PG, CR0_PE
273 	 * Set by cpu_setregs: CR0_NE, CR0_MP, CR0_TS, CR0_WP, CR0_AM
274 	 */
275 	cr0 = rcr0();
276 	cr0 &= ~(CR0_CD | CR0_NW | CR0_EM);
277 	load_cr0(cr0);
278 
279 	amd64_conf_fast_syscall();
280 
281 	/* signal our startup to the BSP. */
282 	mp_naps++;
283 
284 	/* Spin until the BSP releases the AP's. */
285 	while (atomic_load_acq_int(&aps_ready) == 0)
286 		ia32_pause();
287 
288 	init_secondary_tail();
289 }
290 
291 /*******************************************************************
292  * local functions and data
293  */
294 
295 #ifdef NUMA
296 static void
297 mp_realloc_pcpu(int cpuid, int domain)
298 {
299 	vm_page_t m;
300 	vm_offset_t oa, na;
301 
302 	oa = (vm_offset_t)&__pcpu[cpuid];
303 	if (vm_phys_domain(pmap_kextract(oa)) == domain)
304 		return;
305 	m = vm_page_alloc_noobj_domain(domain, 0);
306 	if (m == NULL)
307 		return;
308 	na = PHYS_TO_DMAP(VM_PAGE_TO_PHYS(m));
309 	pagecopy((void *)oa, (void *)na);
310 	pmap_qenter((vm_offset_t)&__pcpu[cpuid], &m, 1);
311 	/* XXX old pcpu page leaked. */
312 }
313 #endif
314 
315 /*
316  * start each AP in our list
317  */
318 int
319 start_all_aps(void)
320 {
321 	vm_page_t m_boottramp, m_pml4, m_pdp, m_pd[4];
322 	pml5_entry_t old_pml45;
323 	pml4_entry_t *v_pml4;
324 	pdp_entry_t *v_pdp;
325 	pd_entry_t *v_pd;
326 	vm_paddr_t boot_address;
327 	u_int32_t mpbioswarmvec;
328 	int apic_id, cpu, domain, i;
329 	u_char mpbiosreason;
330 
331 	mtx_init(&ap_boot_mtx, "ap boot", NULL, MTX_SPIN);
332 
333 	MPASS(bootMP_size <= PAGE_SIZE);
334 	m_boottramp = vm_page_alloc_noobj_contig(0, 1, 0,
335 	    (1ULL << 20), /* Trampoline should be below 1M for real mode */
336 	    PAGE_SIZE, 0, VM_MEMATTR_DEFAULT);
337 	boot_address = VM_PAGE_TO_PHYS(m_boottramp);
338 
339 	/* Create a transient 1:1 mapping of low 4G */
340 	if (la57) {
341 		m_pml4 = pmap_page_alloc_below_4g(true);
342 		v_pml4 = (pml4_entry_t *)PHYS_TO_DMAP(VM_PAGE_TO_PHYS(m_pml4));
343 	} else {
344 		v_pml4 = &kernel_pmap->pm_pmltop[0];
345 	}
346 	m_pdp = pmap_page_alloc_below_4g(true);
347 	v_pdp = (pdp_entry_t *)PHYS_TO_DMAP(VM_PAGE_TO_PHYS(m_pdp));
348 	m_pd[0] = pmap_page_alloc_below_4g(false);
349 	v_pd = (pd_entry_t *)PHYS_TO_DMAP(VM_PAGE_TO_PHYS(m_pd[0]));
350 	for (i = 0; i < NPDEPG; i++)
351 		v_pd[i] = (i << PDRSHIFT) | X86_PG_V | X86_PG_RW | X86_PG_A |
352 		    X86_PG_M | PG_PS;
353 	m_pd[1] = pmap_page_alloc_below_4g(false);
354 	v_pd = (pd_entry_t *)PHYS_TO_DMAP(VM_PAGE_TO_PHYS(m_pd[1]));
355 	for (i = 0; i < NPDEPG; i++)
356 		v_pd[i] = (NBPDP + (i << PDRSHIFT)) | X86_PG_V | X86_PG_RW |
357 		    X86_PG_A | X86_PG_M | PG_PS;
358 	m_pd[2] = pmap_page_alloc_below_4g(false);
359 	v_pd = (pd_entry_t *)PHYS_TO_DMAP(VM_PAGE_TO_PHYS(m_pd[2]));
360 	for (i = 0; i < NPDEPG; i++)
361 		v_pd[i] = (2UL * NBPDP + (i << PDRSHIFT)) | X86_PG_V |
362 		    X86_PG_RW | X86_PG_A | X86_PG_M | PG_PS;
363 	m_pd[3] = pmap_page_alloc_below_4g(false);
364 	v_pd = (pd_entry_t *)PHYS_TO_DMAP(VM_PAGE_TO_PHYS(m_pd[3]));
365 	for (i = 0; i < NPDEPG; i++)
366 		v_pd[i] = (3UL * NBPDP + (i << PDRSHIFT)) | X86_PG_V |
367 		    X86_PG_RW | X86_PG_A | X86_PG_M | PG_PS;
368 	v_pdp[0] = VM_PAGE_TO_PHYS(m_pd[0]) | X86_PG_V |
369 	    X86_PG_RW | X86_PG_A | X86_PG_M;
370 	v_pdp[1] = VM_PAGE_TO_PHYS(m_pd[1]) | X86_PG_V |
371 	    X86_PG_RW | X86_PG_A | X86_PG_M;
372 	v_pdp[2] = VM_PAGE_TO_PHYS(m_pd[2]) | X86_PG_V |
373 	    X86_PG_RW | X86_PG_A | X86_PG_M;
374 	v_pdp[3] = VM_PAGE_TO_PHYS(m_pd[3]) | X86_PG_V |
375 	    X86_PG_RW | X86_PG_A | X86_PG_M;
376 	old_pml45 = kernel_pmap->pm_pmltop[0];
377 	if (la57) {
378 		kernel_pmap->pm_pmltop[0] = VM_PAGE_TO_PHYS(m_pml4) |
379 		    X86_PG_V | X86_PG_RW | X86_PG_A | X86_PG_M;
380 	}
381 	v_pml4[0] = VM_PAGE_TO_PHYS(m_pdp) | X86_PG_V |
382 	    X86_PG_RW | X86_PG_A | X86_PG_M;
383 	pmap_invalidate_all(kernel_pmap);
384 
385 	/* copy the AP 1st level boot code */
386 	bcopy(mptramp_start, (void *)PHYS_TO_DMAP(boot_address), bootMP_size);
387 	if (bootverbose)
388 		printf("AP boot address %#lx\n", boot_address);
389 
390 	/* save the current value of the warm-start vector */
391 	if (!efi_boot)
392 		mpbioswarmvec = *((u_int32_t *) WARMBOOT_OFF);
393 	outb(CMOS_REG, BIOS_RESET);
394 	mpbiosreason = inb(CMOS_DATA);
395 
396 	/* setup a vector to our boot code */
397 	if (!efi_boot) {
398 		*((volatile u_short *)WARMBOOT_OFF) = WARMBOOT_TARGET;
399 		*((volatile u_short *)WARMBOOT_SEG) = (boot_address >> 4);
400 	}
401 	outb(CMOS_REG, BIOS_RESET);
402 	outb(CMOS_DATA, BIOS_WARM);	/* 'warm-start' */
403 
404 	/* Relocate pcpu areas to the correct domain. */
405 #ifdef NUMA
406 	if (vm_ndomains > 1)
407 		for (cpu = 1; cpu < mp_ncpus; cpu++) {
408 			apic_id = cpu_apic_ids[cpu];
409 			domain = acpi_pxm_get_cpu_locality(apic_id);
410 			mp_realloc_pcpu(cpu, domain);
411 		}
412 #endif
413 
414 	/* start each AP */
415 	domain = 0;
416 	for (cpu = 1; cpu < mp_ncpus; cpu++) {
417 		apic_id = cpu_apic_ids[cpu];
418 #ifdef NUMA
419 		if (vm_ndomains > 1)
420 			domain = acpi_pxm_get_cpu_locality(apic_id);
421 #endif
422 		/* allocate and set up an idle stack data page */
423 		bootstacks[cpu] = kmem_malloc(kstack_pages * PAGE_SIZE,
424 		    M_WAITOK | M_ZERO);
425 		doublefault_stack = kmem_malloc(DBLFAULT_STACK_SIZE,
426 		    M_WAITOK | M_ZERO);
427 		mce_stack = kmem_malloc(MCE_STACK_SIZE,
428 		    M_WAITOK | M_ZERO);
429 		nmi_stack = kmem_malloc_domainset(
430 		    DOMAINSET_PREF(domain), NMI_STACK_SIZE, M_WAITOK | M_ZERO);
431 		dbg_stack = kmem_malloc_domainset(
432 		    DOMAINSET_PREF(domain), DBG_STACK_SIZE, M_WAITOK | M_ZERO);
433 		dpcpu = kmem_malloc_domainset(DOMAINSET_PREF(domain),
434 		    DPCPU_SIZE, M_WAITOK | M_ZERO);
435 
436 		bootpcpu = &__pcpu[cpu];
437 		bootSTK = (char *)bootstacks[cpu] +
438 		    kstack_pages * PAGE_SIZE - 8;
439 		bootAP = cpu;
440 
441 		/* attempt to start the Application Processor */
442 		if (!start_ap(apic_id, boot_address)) {
443 			/* restore the warmstart vector */
444 			if (!efi_boot)
445 				*(u_int32_t *)WARMBOOT_OFF = mpbioswarmvec;
446 			panic("AP #%d (PHY# %d) failed!", cpu, apic_id);
447 		}
448 
449 		CPU_SET(cpu, &all_cpus);	/* record AP in CPU map */
450 	}
451 
452 	/* restore the warmstart vector */
453 	if (!efi_boot)
454 		*(u_int32_t *)WARMBOOT_OFF = mpbioswarmvec;
455 
456 	outb(CMOS_REG, BIOS_RESET);
457 	outb(CMOS_DATA, mpbiosreason);
458 
459 	/* Destroy transient 1:1 mapping */
460 	kernel_pmap->pm_pmltop[0] = old_pml45;
461 	invlpg(0);
462 	if (la57)
463 		vm_page_free(m_pml4);
464 	vm_page_free(m_pd[3]);
465 	vm_page_free(m_pd[2]);
466 	vm_page_free(m_pd[1]);
467 	vm_page_free(m_pd[0]);
468 	vm_page_free(m_pdp);
469 	vm_page_free(m_boottramp);
470 
471 	/* number of APs actually started */
472 	return (mp_naps);
473 }
474 
475 /*
476  * This function starts the AP (application processor) identified
477  * by the APIC ID 'physicalCpu'.  It does quite a "song and dance"
478  * to accomplish this.  This is necessary because of the nuances
479  * of the different hardware we might encounter.  It isn't pretty,
480  * but it seems to work.
481  */
482 static int
483 start_ap(int apic_id, vm_paddr_t boot_address)
484 {
485 	int vector, ms;
486 	int cpus;
487 
488 	/* calculate the vector */
489 	vector = (boot_address >> 12) & 0xff;
490 
491 	/* used as a watchpoint to signal AP startup */
492 	cpus = mp_naps;
493 
494 	ipi_startup(apic_id, vector);
495 
496 	/* Wait up to 5 seconds for it to start. */
497 	for (ms = 0; ms < 5000; ms++) {
498 		if (mp_naps > cpus)
499 			return 1;	/* return SUCCESS */
500 		DELAY(1000);
501 	}
502 	return 0;		/* return FAILURE */
503 }
504 
505 /*
506  * Flush the TLB on other CPU's
507  */
508 
509 /*
510  * Invalidation request.  PCPU pc_smp_tlb_op uses u_int instead of the
511  * enum to avoid both namespace and ABI issues (with enums).
512  */
513 enum invl_op_codes {
514       INVL_OP_TLB		= 1,
515       INVL_OP_TLB_INVPCID	= 2,
516       INVL_OP_TLB_INVPCID_PTI	= 3,
517       INVL_OP_TLB_PCID		= 4,
518       INVL_OP_PGRNG		= 5,
519       INVL_OP_PGRNG_INVPCID	= 6,
520       INVL_OP_PGRNG_PCID	= 7,
521       INVL_OP_PG		= 8,
522       INVL_OP_PG_INVPCID	= 9,
523       INVL_OP_PG_PCID		= 10,
524       INVL_OP_CACHE		= 11,
525 };
526 
527 /*
528  * These variables are initialized at startup to reflect how each of
529  * the different kinds of invalidations should be performed on the
530  * current machine and environment.
531  */
532 static enum invl_op_codes invl_op_tlb;
533 static enum invl_op_codes invl_op_pgrng;
534 static enum invl_op_codes invl_op_pg;
535 
536 /*
537  * Scoreboard of IPI completion notifications from target to IPI initiator.
538  *
539  * Each CPU can initiate shootdown IPI independently from other CPUs.
540  * Initiator enters critical section, then fills its local PCPU
541  * shootdown info (pc_smp_tlb_ vars), then clears scoreboard generation
542  * at location (cpu, my_cpuid) for each target cpu.  After that IPI is
543  * sent to all targets which scan for zeroed scoreboard generation
544  * words.  Upon finding such word the shootdown data is read from
545  * corresponding cpu's pcpu, and generation is set.  Meantime initiator
546  * loops waiting for all zeroed generations in scoreboard to update.
547  */
548 static uint32_t *invl_scoreboard;
549 
550 static void
551 invl_scoreboard_init(void *arg __unused)
552 {
553 	u_int i;
554 
555 	invl_scoreboard = malloc(sizeof(uint32_t) * (mp_maxid + 1) *
556 	    (mp_maxid + 1), M_DEVBUF, M_WAITOK);
557 	for (i = 0; i < (mp_maxid + 1) * (mp_maxid + 1); i++)
558 		invl_scoreboard[i] = 1;
559 
560 	if (pmap_pcid_enabled) {
561 		if (invpcid_works) {
562 			if (pti)
563 				invl_op_tlb = INVL_OP_TLB_INVPCID_PTI;
564 			else
565 				invl_op_tlb = INVL_OP_TLB_INVPCID;
566 			invl_op_pgrng = INVL_OP_PGRNG_INVPCID;
567 			invl_op_pg = INVL_OP_PG_INVPCID;
568 		} else {
569 			invl_op_tlb = INVL_OP_TLB_PCID;
570 			invl_op_pgrng = INVL_OP_PGRNG_PCID;
571 			invl_op_pg = INVL_OP_PG_PCID;
572 		}
573 	} else {
574 		invl_op_tlb = INVL_OP_TLB;
575 		invl_op_pgrng = INVL_OP_PGRNG;
576 		invl_op_pg = INVL_OP_PG;
577 	}
578 }
579 SYSINIT(invl_ops, SI_SUB_SMP - 1, SI_ORDER_ANY, invl_scoreboard_init, NULL);
580 
581 static uint32_t *
582 invl_scoreboard_getcpu(u_int cpu)
583 {
584 	return (invl_scoreboard + cpu * (mp_maxid + 1));
585 }
586 
587 static uint32_t *
588 invl_scoreboard_slot(u_int cpu)
589 {
590 	return (invl_scoreboard_getcpu(cpu) + PCPU_GET(cpuid));
591 }
592 
593 /*
594  * Used by the pmap to request cache or TLB invalidation on local and
595  * remote processors.  Mask provides the set of remote CPUs that are
596  * to be signalled with the invalidation IPI.  As an optimization, the
597  * curcpu_cb callback is invoked on the calling CPU in a critical
598  * section while waiting for the remote CPUs to complete the operation.
599  *
600  * The callback function is called unconditionally on the caller's
601  * underlying processor, even when this processor is not set in the
602  * mask.  So, the callback function must be prepared to handle such
603  * spurious invocations.
604  *
605  * Interrupts must be enabled when calling the function with smp
606  * started, to avoid deadlock with other IPIs that are protected with
607  * smp_ipi_mtx spinlock at the initiator side.
608  *
609  * Function must be called with the thread pinned, and it unpins on
610  * completion.
611  */
612 static void
613 smp_targeted_tlb_shootdown(pmap_t pmap, vm_offset_t addr1, vm_offset_t addr2,
614     smp_invl_cb_t curcpu_cb, enum invl_op_codes op)
615 {
616 	cpuset_t mask;
617 	uint32_t generation, *p_cpudone;
618 	int cpu;
619 	bool is_all;
620 
621 	/*
622 	 * It is not necessary to signal other CPUs while booting or
623 	 * when in the debugger.
624 	 */
625 	if (__predict_false(kdb_active || KERNEL_PANICKED() || !smp_started))
626 		goto local_cb;
627 
628 	KASSERT(curthread->td_pinned > 0, ("curthread not pinned"));
629 
630 	/*
631 	 * Make a stable copy of the set of CPUs on which the pmap is active.
632 	 * See if we have to interrupt other CPUs.
633 	 */
634 	CPU_COPY(pmap_invalidate_cpu_mask(pmap), &mask);
635 	is_all = CPU_CMP(&mask, &all_cpus) == 0;
636 	CPU_CLR(curcpu, &mask);
637 	if (CPU_EMPTY(&mask))
638 		goto local_cb;
639 
640 	/*
641 	 * Initiator must have interrupts enabled, which prevents
642 	 * non-invalidation IPIs that take smp_ipi_mtx spinlock,
643 	 * from deadlocking with us.  On the other hand, preemption
644 	 * must be disabled to pin initiator to the instance of the
645 	 * pcpu pc_smp_tlb data and scoreboard line.
646 	 */
647 	KASSERT((read_rflags() & PSL_I) != 0,
648 	    ("smp_targeted_tlb_shootdown: interrupts disabled"));
649 	critical_enter();
650 
651 	PCPU_SET(smp_tlb_addr1, addr1);
652 	PCPU_SET(smp_tlb_addr2, addr2);
653 	PCPU_SET(smp_tlb_pmap, pmap);
654 	generation = PCPU_GET(smp_tlb_gen);
655 	if (++generation == 0)
656 		generation = 1;
657 	PCPU_SET(smp_tlb_gen, generation);
658 	PCPU_SET(smp_tlb_op, op);
659 	/* Fence between filling smp_tlb fields and clearing scoreboard. */
660 	atomic_thread_fence_rel();
661 
662 	CPU_FOREACH_ISSET(cpu, &mask) {
663 		KASSERT(*invl_scoreboard_slot(cpu) != 0,
664 		    ("IPI scoreboard is zero, initiator %d target %d",
665 		    curcpu, cpu));
666 		*invl_scoreboard_slot(cpu) = 0;
667 	}
668 
669 	/*
670 	 * IPI acts as a fence between writing to the scoreboard above
671 	 * (zeroing slot) and reading from it below (wait for
672 	 * acknowledgment).
673 	 */
674 	if (is_all) {
675 		ipi_all_but_self(IPI_INVLOP);
676 	} else {
677 		ipi_selected(mask, IPI_INVLOP);
678 	}
679 	curcpu_cb(pmap, addr1, addr2);
680 	CPU_FOREACH_ISSET(cpu, &mask) {
681 		p_cpudone = invl_scoreboard_slot(cpu);
682 		while (atomic_load_int(p_cpudone) != generation)
683 			ia32_pause();
684 	}
685 
686 	/*
687 	 * Unpin before leaving critical section.  If the thread owes
688 	 * preemption, this allows scheduler to select thread on any
689 	 * CPU from its cpuset.
690 	 */
691 	sched_unpin();
692 	critical_exit();
693 
694 	return;
695 
696 local_cb:
697 	critical_enter();
698 	curcpu_cb(pmap, addr1, addr2);
699 	sched_unpin();
700 	critical_exit();
701 }
702 
703 void
704 smp_masked_invltlb(pmap_t pmap, smp_invl_cb_t curcpu_cb)
705 {
706 	smp_targeted_tlb_shootdown(pmap, 0, 0, curcpu_cb, invl_op_tlb);
707 #ifdef COUNT_XINVLTLB_HITS
708 	ipi_global++;
709 #endif
710 }
711 
712 void
713 smp_masked_invlpg(vm_offset_t addr, pmap_t pmap, smp_invl_cb_t curcpu_cb)
714 {
715 	smp_targeted_tlb_shootdown(pmap, addr, 0, curcpu_cb, invl_op_pg);
716 #ifdef COUNT_XINVLTLB_HITS
717 	ipi_page++;
718 #endif
719 }
720 
721 void
722 smp_masked_invlpg_range(vm_offset_t addr1, vm_offset_t addr2, pmap_t pmap,
723     smp_invl_cb_t curcpu_cb)
724 {
725 	smp_targeted_tlb_shootdown(pmap, addr1, addr2, curcpu_cb,
726 	    invl_op_pgrng);
727 #ifdef COUNT_XINVLTLB_HITS
728 	ipi_range++;
729 	ipi_range_size += (addr2 - addr1) / PAGE_SIZE;
730 #endif
731 }
732 
733 void
734 smp_cache_flush(smp_invl_cb_t curcpu_cb)
735 {
736 	smp_targeted_tlb_shootdown(kernel_pmap, 0, 0, curcpu_cb, INVL_OP_CACHE);
737 }
738 
739 /*
740  * Handlers for TLB related IPIs
741  */
742 static void
743 invltlb_handler(pmap_t smp_tlb_pmap)
744 {
745 #ifdef COUNT_XINVLTLB_HITS
746 	xhits_gbl[PCPU_GET(cpuid)]++;
747 #endif /* COUNT_XINVLTLB_HITS */
748 #ifdef COUNT_IPIS
749 	(*ipi_invltlb_counts[PCPU_GET(cpuid)])++;
750 #endif /* COUNT_IPIS */
751 
752 	if (smp_tlb_pmap == kernel_pmap)
753 		invltlb_glob();
754 	else
755 		invltlb();
756 }
757 
758 static void
759 invltlb_invpcid_handler(pmap_t smp_tlb_pmap)
760 {
761 	struct invpcid_descr d;
762 
763 #ifdef COUNT_XINVLTLB_HITS
764 	xhits_gbl[PCPU_GET(cpuid)]++;
765 #endif /* COUNT_XINVLTLB_HITS */
766 #ifdef COUNT_IPIS
767 	(*ipi_invltlb_counts[PCPU_GET(cpuid)])++;
768 #endif /* COUNT_IPIS */
769 
770 	d.pcid = smp_tlb_pmap->pm_pcids[PCPU_GET(cpuid)].pm_pcid;
771 	d.pad = 0;
772 	d.addr = 0;
773 	invpcid(&d, smp_tlb_pmap == kernel_pmap ? INVPCID_CTXGLOB :
774 	    INVPCID_CTX);
775 }
776 
777 static void
778 invltlb_invpcid_pti_handler(pmap_t smp_tlb_pmap)
779 {
780 	struct invpcid_descr d;
781 
782 #ifdef COUNT_XINVLTLB_HITS
783 	xhits_gbl[PCPU_GET(cpuid)]++;
784 #endif /* COUNT_XINVLTLB_HITS */
785 #ifdef COUNT_IPIS
786 	(*ipi_invltlb_counts[PCPU_GET(cpuid)])++;
787 #endif /* COUNT_IPIS */
788 
789 	d.pcid = smp_tlb_pmap->pm_pcids[PCPU_GET(cpuid)].pm_pcid;
790 	d.pad = 0;
791 	d.addr = 0;
792 	if (smp_tlb_pmap == kernel_pmap) {
793 		/*
794 		 * This invalidation actually needs to clear kernel
795 		 * mappings from the TLB in the current pmap, but
796 		 * since we were asked for the flush in the kernel
797 		 * pmap, achieve it by performing global flush.
798 		 */
799 		invpcid(&d, INVPCID_CTXGLOB);
800 	} else {
801 		invpcid(&d, INVPCID_CTX);
802 		if (smp_tlb_pmap == PCPU_GET(curpmap) &&
803 		    smp_tlb_pmap->pm_ucr3 != PMAP_NO_CR3)
804 			PCPU_SET(ucr3_load_mask, ~CR3_PCID_SAVE);
805 	}
806 }
807 
808 static void
809 invltlb_pcid_handler(pmap_t smp_tlb_pmap)
810 {
811 	uint32_t pcid;
812 
813 #ifdef COUNT_XINVLTLB_HITS
814 	xhits_gbl[PCPU_GET(cpuid)]++;
815 #endif /* COUNT_XINVLTLB_HITS */
816 #ifdef COUNT_IPIS
817 	(*ipi_invltlb_counts[PCPU_GET(cpuid)])++;
818 #endif /* COUNT_IPIS */
819 
820 	if (smp_tlb_pmap == kernel_pmap) {
821 		invltlb_glob();
822 	} else {
823 		/*
824 		 * The current pmap might not be equal to
825 		 * smp_tlb_pmap.  The clearing of the pm_gen in
826 		 * pmap_invalidate_all() takes care of TLB
827 		 * invalidation when switching to the pmap on this
828 		 * CPU.
829 		 */
830 		if (smp_tlb_pmap == PCPU_GET(curpmap)) {
831 			pcid = smp_tlb_pmap->pm_pcids[PCPU_GET(cpuid)].pm_pcid;
832 			load_cr3(smp_tlb_pmap->pm_cr3 | pcid);
833 			if (smp_tlb_pmap->pm_ucr3 != PMAP_NO_CR3)
834 				PCPU_SET(ucr3_load_mask, ~CR3_PCID_SAVE);
835 		}
836 	}
837 }
838 
839 static void
840 invlpg_handler(vm_offset_t smp_tlb_addr1)
841 {
842 #ifdef COUNT_XINVLTLB_HITS
843 	xhits_pg[PCPU_GET(cpuid)]++;
844 #endif /* COUNT_XINVLTLB_HITS */
845 #ifdef COUNT_IPIS
846 	(*ipi_invlpg_counts[PCPU_GET(cpuid)])++;
847 #endif /* COUNT_IPIS */
848 
849 	invlpg(smp_tlb_addr1);
850 }
851 
852 static void
853 invlpg_invpcid_handler(pmap_t smp_tlb_pmap, vm_offset_t smp_tlb_addr1)
854 {
855 	struct invpcid_descr d;
856 
857 #ifdef COUNT_XINVLTLB_HITS
858 	xhits_pg[PCPU_GET(cpuid)]++;
859 #endif /* COUNT_XINVLTLB_HITS */
860 #ifdef COUNT_IPIS
861 	(*ipi_invlpg_counts[PCPU_GET(cpuid)])++;
862 #endif /* COUNT_IPIS */
863 
864 	pmap_invlpg(smp_tlb_pmap, smp_tlb_addr1);
865 	if (smp_tlb_pmap == PCPU_GET(curpmap) &&
866 	    smp_tlb_pmap->pm_ucr3 != PMAP_NO_CR3 &&
867 	    PCPU_GET(ucr3_load_mask) == PMAP_UCR3_NOMASK) {
868 		d.pcid = smp_tlb_pmap->pm_pcids[PCPU_GET(cpuid)].pm_pcid |
869 		    PMAP_PCID_USER_PT;
870 		d.pad = 0;
871 		d.addr = smp_tlb_addr1;
872 		invpcid(&d, INVPCID_ADDR);
873 	}
874 }
875 
876 static void
877 invlpg_pcid_handler(pmap_t smp_tlb_pmap, vm_offset_t smp_tlb_addr1)
878 {
879 	uint64_t kcr3, ucr3;
880 	uint32_t pcid;
881 
882 #ifdef COUNT_XINVLTLB_HITS
883 	xhits_pg[PCPU_GET(cpuid)]++;
884 #endif /* COUNT_XINVLTLB_HITS */
885 #ifdef COUNT_IPIS
886 	(*ipi_invlpg_counts[PCPU_GET(cpuid)])++;
887 #endif /* COUNT_IPIS */
888 
889 	invlpg(smp_tlb_addr1);
890 	if (smp_tlb_pmap == PCPU_GET(curpmap) &&
891 	    (ucr3 = smp_tlb_pmap->pm_ucr3) != PMAP_NO_CR3 &&
892 	    PCPU_GET(ucr3_load_mask) == PMAP_UCR3_NOMASK) {
893 		pcid = smp_tlb_pmap->pm_pcids[PCPU_GET(cpuid)].pm_pcid;
894 		kcr3 = smp_tlb_pmap->pm_cr3 | pcid | CR3_PCID_SAVE;
895 		ucr3 |= pcid | PMAP_PCID_USER_PT | CR3_PCID_SAVE;
896 		pmap_pti_pcid_invlpg(ucr3, kcr3, smp_tlb_addr1);
897 	}
898 }
899 
900 static void
901 invlrng_handler(vm_offset_t smp_tlb_addr1, vm_offset_t smp_tlb_addr2)
902 {
903 	vm_offset_t addr;
904 
905 #ifdef COUNT_XINVLTLB_HITS
906 	xhits_rng[PCPU_GET(cpuid)]++;
907 #endif /* COUNT_XINVLTLB_HITS */
908 #ifdef COUNT_IPIS
909 	(*ipi_invlrng_counts[PCPU_GET(cpuid)])++;
910 #endif /* COUNT_IPIS */
911 
912 	addr = smp_tlb_addr1;
913 	do {
914 		invlpg(addr);
915 		addr += PAGE_SIZE;
916 	} while (addr < smp_tlb_addr2);
917 }
918 
919 static void
920 invlrng_invpcid_handler(pmap_t smp_tlb_pmap, vm_offset_t smp_tlb_addr1,
921     vm_offset_t smp_tlb_addr2)
922 {
923 	struct invpcid_descr d;
924 	vm_offset_t addr;
925 
926 #ifdef COUNT_XINVLTLB_HITS
927 	xhits_rng[PCPU_GET(cpuid)]++;
928 #endif /* COUNT_XINVLTLB_HITS */
929 #ifdef COUNT_IPIS
930 	(*ipi_invlrng_counts[PCPU_GET(cpuid)])++;
931 #endif /* COUNT_IPIS */
932 
933 	addr = smp_tlb_addr1;
934 	if (smp_tlb_pmap == kernel_pmap && PCPU_GET(pcid_invlpg_workaround)) {
935 		struct invpcid_descr d = { 0 };
936 
937 		invpcid(&d, INVPCID_CTXGLOB);
938 	} else {
939 		do {
940 			invlpg(addr);
941 			addr += PAGE_SIZE;
942 		} while (addr < smp_tlb_addr2);
943 	}
944 	if (smp_tlb_pmap == PCPU_GET(curpmap) &&
945 	    smp_tlb_pmap->pm_ucr3 != PMAP_NO_CR3 &&
946 	    PCPU_GET(ucr3_load_mask) == PMAP_UCR3_NOMASK) {
947 		d.pcid = smp_tlb_pmap->pm_pcids[PCPU_GET(cpuid)].pm_pcid |
948 		    PMAP_PCID_USER_PT;
949 		d.pad = 0;
950 		d.addr = smp_tlb_addr1;
951 		do {
952 			invpcid(&d, INVPCID_ADDR);
953 			d.addr += PAGE_SIZE;
954 		} while (d.addr < smp_tlb_addr2);
955 	}
956 }
957 
958 static void
959 invlrng_pcid_handler(pmap_t smp_tlb_pmap, vm_offset_t smp_tlb_addr1,
960     vm_offset_t smp_tlb_addr2)
961 {
962 	vm_offset_t addr;
963 	uint64_t kcr3, ucr3;
964 	uint32_t pcid;
965 
966 #ifdef COUNT_XINVLTLB_HITS
967 	xhits_rng[PCPU_GET(cpuid)]++;
968 #endif /* COUNT_XINVLTLB_HITS */
969 #ifdef COUNT_IPIS
970 	(*ipi_invlrng_counts[PCPU_GET(cpuid)])++;
971 #endif /* COUNT_IPIS */
972 
973 	addr = smp_tlb_addr1;
974 	do {
975 		invlpg(addr);
976 		addr += PAGE_SIZE;
977 	} while (addr < smp_tlb_addr2);
978 	if (smp_tlb_pmap == PCPU_GET(curpmap) &&
979 	    (ucr3 = smp_tlb_pmap->pm_ucr3) != PMAP_NO_CR3 &&
980 	    PCPU_GET(ucr3_load_mask) == PMAP_UCR3_NOMASK) {
981 		pcid = smp_tlb_pmap->pm_pcids[PCPU_GET(cpuid)].pm_pcid;
982 		kcr3 = smp_tlb_pmap->pm_cr3 | pcid | CR3_PCID_SAVE;
983 		ucr3 |= pcid | PMAP_PCID_USER_PT | CR3_PCID_SAVE;
984 		pmap_pti_pcid_invlrng(ucr3, kcr3, smp_tlb_addr1, smp_tlb_addr2);
985 	}
986 }
987 
988 static void
989 invlcache_handler(void)
990 {
991 #ifdef COUNT_IPIS
992 	(*ipi_invlcache_counts[PCPU_GET(cpuid)])++;
993 #endif /* COUNT_IPIS */
994 	wbinvd();
995 }
996 
997 static void
998 invlop_handler_one_req(enum invl_op_codes smp_tlb_op, pmap_t smp_tlb_pmap,
999     vm_offset_t smp_tlb_addr1, vm_offset_t smp_tlb_addr2)
1000 {
1001 	switch (smp_tlb_op) {
1002 	case INVL_OP_TLB:
1003 		invltlb_handler(smp_tlb_pmap);
1004 		break;
1005 	case INVL_OP_TLB_INVPCID:
1006 		invltlb_invpcid_handler(smp_tlb_pmap);
1007 		break;
1008 	case INVL_OP_TLB_INVPCID_PTI:
1009 		invltlb_invpcid_pti_handler(smp_tlb_pmap);
1010 		break;
1011 	case INVL_OP_TLB_PCID:
1012 		invltlb_pcid_handler(smp_tlb_pmap);
1013 		break;
1014 	case INVL_OP_PGRNG:
1015 		invlrng_handler(smp_tlb_addr1, smp_tlb_addr2);
1016 		break;
1017 	case INVL_OP_PGRNG_INVPCID:
1018 		invlrng_invpcid_handler(smp_tlb_pmap, smp_tlb_addr1,
1019 		    smp_tlb_addr2);
1020 		break;
1021 	case INVL_OP_PGRNG_PCID:
1022 		invlrng_pcid_handler(smp_tlb_pmap, smp_tlb_addr1,
1023 		    smp_tlb_addr2);
1024 		break;
1025 	case INVL_OP_PG:
1026 		invlpg_handler(smp_tlb_addr1);
1027 		break;
1028 	case INVL_OP_PG_INVPCID:
1029 		invlpg_invpcid_handler(smp_tlb_pmap, smp_tlb_addr1);
1030 		break;
1031 	case INVL_OP_PG_PCID:
1032 		invlpg_pcid_handler(smp_tlb_pmap, smp_tlb_addr1);
1033 		break;
1034 	case INVL_OP_CACHE:
1035 		invlcache_handler();
1036 		break;
1037 	default:
1038 		__assert_unreachable();
1039 		break;
1040 	}
1041 }
1042 
1043 void
1044 invlop_handler(void)
1045 {
1046 	struct pcpu *initiator_pc;
1047 	pmap_t smp_tlb_pmap;
1048 	vm_offset_t smp_tlb_addr1, smp_tlb_addr2;
1049 	u_int initiator_cpu_id;
1050 	enum invl_op_codes smp_tlb_op;
1051 	uint32_t *scoreboard, smp_tlb_gen;
1052 
1053 	scoreboard = invl_scoreboard_getcpu(PCPU_GET(cpuid));
1054 	for (;;) {
1055 		for (initiator_cpu_id = 0; initiator_cpu_id <= mp_maxid;
1056 		    initiator_cpu_id++) {
1057 			if (atomic_load_int(&scoreboard[initiator_cpu_id]) == 0)
1058 				break;
1059 		}
1060 		if (initiator_cpu_id > mp_maxid)
1061 			break;
1062 		initiator_pc = cpuid_to_pcpu[initiator_cpu_id];
1063 
1064 		/*
1065 		 * This acquire fence and its corresponding release
1066 		 * fence in smp_targeted_tlb_shootdown() is between
1067 		 * reading zero scoreboard slot and accessing PCPU of
1068 		 * initiator for pc_smp_tlb values.
1069 		 */
1070 		atomic_thread_fence_acq();
1071 		smp_tlb_pmap = initiator_pc->pc_smp_tlb_pmap;
1072 		smp_tlb_addr1 = initiator_pc->pc_smp_tlb_addr1;
1073 		smp_tlb_addr2 = initiator_pc->pc_smp_tlb_addr2;
1074 		smp_tlb_op = initiator_pc->pc_smp_tlb_op;
1075 		smp_tlb_gen = initiator_pc->pc_smp_tlb_gen;
1076 
1077 		/*
1078 		 * Ensure that we do not make our scoreboard
1079 		 * notification visible to the initiator until the
1080 		 * pc_smp_tlb values are read.  The corresponding
1081 		 * fence is implicitly provided by the barrier in the
1082 		 * IPI send operation before the APIC ICR register
1083 		 * write.
1084 		 *
1085 		 * As an optimization, the request is acknowledged
1086 		 * before the actual invalidation is performed.  It is
1087 		 * safe because target CPU cannot return to userspace
1088 		 * before handler finishes. Only NMI can preempt the
1089 		 * handler, but NMI would see the kernel handler frame
1090 		 * and not touch not-invalidated user page table.
1091 		 */
1092 		atomic_thread_fence_acq();
1093 		atomic_store_int(&scoreboard[initiator_cpu_id], smp_tlb_gen);
1094 
1095 		invlop_handler_one_req(smp_tlb_op, smp_tlb_pmap, smp_tlb_addr1,
1096 		    smp_tlb_addr2);
1097 	}
1098 }
1099